1. Field of the Invention
The present invention relates to straddle-type vehicles, and more particularly, to a bracket that couples a down frame with an engine.
2. Description of the Related Art
Straddle-type vehicles include motorcycles, for example. Motorcycles are disclosed in Japanese Patent No. 4546312, for example.
According to Japanese Patent No. 4546312, a motorcycle includes an engine, a frame, and a plurality of engine brackets. The frame includes a head pipe, a main frame, a down frame, a lower frame, and a pivot frame. The main frame extends rearward from the head pipe. The down frame extends downward from the bottom of the head pipe. The lower frame extends rearward from the bottom of the down frame. The pivot frame couples a rear portion of the lower frame with a rear portion of the main frame. The engine is supported on the frame via the plurality of engine brackets. The plurality of engine brackets include a first engine brake, a second engine bracket and a third engine bracket. The first engine bracket connects the pivot frame with the cylinder head of the engine. The second engine bracket connects the top end of the lower frame with the crankcase of the engine. The third engine bracket connects the portion of the lower frame that is in its middle as measured in a front-to-rear direction thereof, with the crankcase.
A motorcycle may travel over an uneven surface. At this moment, the engine bracket coupling the frame located forward of the engine with the engine (hereinafter referred to as front engine bracket) receives an impact-related load in a front-to-rear direction with respect to the vehicle. To address such a load, it is desirable to reduce the rigidity of the bracket to absorb the impact.
When the motorcycle is cornering, the vehicle, even when leaned, tends to rise up due to centrifugal forces and the rigidity balance of various components. At this moment, the front engine bracket receives a twisting load in a twisting direction. To address such a load in a twisting direction, it is desirable to ensure a high rigidity of the bracket to prevent the engine from rising up due to centrifugal forces.
Thus, the front engine bracket is desired to possess different properties associated with a front-to-rear direction with respect to the vehicle and a twisting direction. The bracket is desired to possess these properties at the same time. Japanese Patent No. 4546312 fails to disclose or suggest the properties that the front engine bracket is desired to possess.